The poisonous spine on a stingray's whip-like tail is one of nature's nastiest creations — up to 17 inches long in some species. Sharp and rigid, it can penetrate a protective boot or even the side of a small boat when launched with the full force of the stingray's muscular tail.
Both sides of the spine are lined with saw-like serrations pointing toward the tip. (See drawing.) While it is very easy for the spine to slice through flesh, attempts to remove it can produce even more extensive tissue damage. It's like trying to pull out a fishhook that has not just one barb but hundreds.
And that's not all. There are two grooves on the ventral side of the spine containing glands that produce venom made up of 5'-nucleotidase, phosphodiesterase, and serotonin, among other components. This venom causes tissue necrosis, especially to muscle and fat. The entire structure is coated with mucus and surrounded by a thin membrane. Even after the apparatus is removed, pieces of the spine and membrane, along with toxin and mucus, can remain, producing a festering chronic ulcer and secondary infection if the wound is not inspected and debrided meticulously.
Pliny the Elder (23–79 A.D.) stated in his Naturalis Historia that “there is nothing that is more to be dreaded than the sting which protrudes from the tail of the Trygon [stingray].” Oppian (172–210 A.D.) wrote a treatise on fishes and fishing that called the stingray “the Pois'nous Fire-Flaire,” and concluded that “of all ills… that Seas produce or earth's dark Womb conceals, none equals that the Ray-like Fire-Flaire bears.” These observations bear witness to the excruciating pain that frequently follows a stingray injury.
Stingrays are generally placid, nonaggressive scavengers who would rather swim away from a threat than attack. They are commonly found in shallow areas of warm ocean waters, partially buried in the sandy bottom. If they are stepped on or brushed up against without warning, a defensive reflex whips their tail up and over their body, striking the victim — most commonly in the leg — and causing a puncture wound or ragged laceration.
Fortunately, stingray-associated fatalities are exceedingly rare. Although there are several thousand stingray injuries reported each year in the United States alone, the number of deaths recorded in the world's medical literature amounts to just a dozen or two. The fatal cardiac wound sustained by TV's “Crocodile Hunter” Steve Irwin in September while snorkeling off Australia was distinctly unusual and bizarre.
But by definition, any stingray-associated fatality will have its bizarre aspects, as in the following remarkable case:
“In 1988, a large ray jumped out of the water over a fast-moving aluminum boat near north Queensland, Australia, striking three people, including a 12-year-old boy who sustained wounds to the left knee and through his left nipple. The child immediately complained of chest pain and difficulty breathing. He was admitted to hospital and discharged the next day when he seemed to be doing well. Symptomatic improvement continued until the sixth day after injury, when he suddenly collapsed and could not be resuscitated. Autopsy showed blood in the pericardial sac and a penetrating wound to the right ventricle. Death was attributed to cardiac tamponade caused by delayed cardiac perforation from the necrotic effects of the stingray's venom.” (Med J Aust 1989;151:621.)
Deaths also have been reported following penetrating abdominal injuries as well as from tetanus and secondary infection after injuries to the extremities. One victim exsanguinated after sustaining a wound to the femoral artery.
The most dramatic initial manifestation of stingray injury is rapid onset of severe pain at the site of the wound. The wound itself, initially dusky and mottled, later becomes erythematous and then necrotic. Pain reaches maximum intensity at about an hour, and can continue for several days if untreated. Systemic signs and symptoms may include tremors, hypotension, diaphoresis, nausea and vomiting, tachycardia, pain-associated muscle spasms, and seizures.
Basic first aid for these injuries involves pain control, wound care, and prophylaxis. Because stingray venom is denatured at elevated temperatures, soaking the wounded area in hot but not scalding water (105–113°F) for up to 90 minutes should provide significant symptomatic relief, which can be supplemented with local or systemic analgesia as needed. The wound should be carefully explored and any foreign material or necrotic tissue debrided thoroughly. The wound is then packed open or sutured loosely.
Antibiotic prophylaxis covering Vibrio species is generally recommended; a fluoroquinolone or trimethoprim/sulfamethoxasole would be an appropriate choice. Tetanus immunization should be brought up to date. Patients with penetrating wounds to the thorax or abdomen need to be referred for prompt surgical exploration; any retained stingray spine should not be removed in the field. Minimally symptomatic patients can be observed for at least four hours before discharge from the emergency department.
The role of radiology in evaluating stingray injuries has not been adequately studied. Plain radiographs of the wound may not show retained foreign material; soft tissue films or MRI would be expected to have greater sensitivity. Ultrasound imaging may be useful, but has not been investigated in either a clinical or experimental setting. The key to minimizing long-term complications remains careful exploration and debridement of the wound itself.
The most effective means of preventing complications from stingray envenomation, of course, is to avoid injury in the first place. In their book, All Stings Considered, Craig Thomas and Susan Scott pointed out that it is not wise to swim over the back of a stingray while snorkeling or scuba diving. They also recommended that when wading in sandy areas where rays may be resting or feeding, one should shuffle, make plenty of commotion, and stir the water and sand ahead with a stick. The rays want to avoid a nasty encounter as much as you do, and will generally swim away.
Management of Stingray Injuries
▪ Immerse affected area in hot water (105–113° F) for 30–90 minutes.
▪ Use local and/or systemic analgesia as needed.
▪ Explore and debride the wound thoroughly.
▪ Allow healing by secondary intention.
▪ Administer prophylactic antibiotics for large, established, or puncture wounds.
▪ Update tetanus prophylaxis.
▪ Refer immediately penetrating wounds of chest or abdomen.
Source: Med J Aust 2001;175:33.